1. Field of the Invention
The present invention relates to an encoder and a decoder using a run-length-limited (RLL) code.
2. Description of the Related Art
For improvement of recording density, data to be stored in/read from a recording medium (such as a magnetic disk or an optical disk) is encoded/decoded according to run length limited (RLL).
There are several types of RLL scheme, each having its own characteristics. For example, an encoding/decoding method disclosed in Japanese Patent Application No. 2004-117239 (filed by the present applicant) realizes a high code rate without violating G constraint and I constraint.
The encoding/decoding method is simple, however, the size of a circuit executing the encoding/decoding method can become large. This is because the encoder/decoder has to process parallel data (for example, 10-bit parallel data) to be stored in/read from the recording medium, while RLL originally assumes a bit string with no structure. Specifically, the encoder/decoder needs to be provided with a plurality of circuits, each corresponding to each bit pattern included in the parallel data. Furthermore, the encoder/decoder needs to perform various types of processing to satisfy a plurality of constraints, thereby further increasing the circuit size.